Transmission overhaul

Oct 21, 2011

We had just anchored our power voyaging boat Passagemaker in a perfect bay on Isle a Vache off the southwest corner of Haiti. I wanted to set the anchor by engaging reverse, but when I shifted the transmission into reverse and applied power, nothing happened.  

Luckily Passagemaker is 50 years old and, with plenty of storage space, we had a brand new spare transmission under the aft companionway ladder. The transmission is a Borg Warner Velvet Drive which, complete with the reduction drive, weighs approximately 120 pounds. Changing the transmission only took about an hour with two of us doing the grunt work.

The next stop was an Internet cafe to assess the size of the dent to the wallet. Simplicity Marine has a great website for complete transmissions and more (www.simplicity-marine.com/velvetdrive-borgwarner.htm). Be prepared for sticker shock as a new transmission is going to set you back anywhere between $3,000 and $5,000 depending on the model.

We decided to open up our unit and see what the problem was before we shelled out that sort of cash. When working on any item, especially mechanical units, you must observe the following rules:

1. Do not be deterred by the so-called specialists who tell you that you need special tools not available to the ordinary person. Most tool kits have everything you will need and if there is some unusual item, go and buy the tool so over the years you build up everything you need.

2. Buy the workshop manual and parts list. Often they can be downloaded from the manufacturers’ websites as PDF files. Even printed ones are well worth the money.

3. Have a clean and spotless area to work in when reassembling so no dirt gets into finely machined valves.

4. Take lots of pictures as you strip the unit down. They will prove invaluable when you reassemble and wonder which way round something went.

5. Buy and use a good torque wrench (which is probably more than the so-called specialist will do!!)

6. Take your time.

We opened our transmission with nothing more than a regular socket set and found the springs holding the reverse plates had somehow come loose and the clutch plates themselves had broken into pieces.

We were lucky that there were no metal filings and tiny pieces floating around which would have necessitated a total strip down. We found all the twisted springs and made sure there were no bits of clutch plates missing. Thus we just had to install new reverse plates and springs and reassemble the unit.

So we decided to buy the manual and the service kit to rebuild the unit. What was the worst that could happen? As with most pieces of equipment, if you run into a problem, provided you haven’t damaged anything opening it up, you can always carry the parts to the specialist to reassemble properly (make sure he shows you what you did wrong). On the other hand, I’m sure you are as intelligent as most mechanics, so you stand a darn good chance of making a success of it.

We found the manual and overhaul kit by going to www.marineengineparts.com and entering the following part numbers: Velvet Drive Marine Transmission Parts and Service Manual (Part # WM1289) $39.69; Transmission Master Overhaul Kit (Part # 18-2591) $189.95.

The Velvet Drive manual will take you step by step through the various processes. Plus for those of us who took Engineering Drawing in school or college, the drawings are works of art in their own right. Incidentally, the manual is not only vital for the rebuilding process, but it also helps you to identify your particular transmission.

Velvet Drive units also have a small info plate on the side to aid in identification. Take care when scraping the paint off.

Strangely, the kit did not include the 11 springs for the reverse pressure plates, which were, however, available from www.firstchoicemarine.com.

When we reassembled the unit we made sure to follow the instructions in the manual on which seals to install dry and which should be lubricated first. We filled the unit with the correct grade of automatic gearbox oil and reinstalled the transmission to make sure it was working well. After everything was in order, we swapped it back out and gave the unit a lovely coat of white paint for that professional look.

The end result was a very straightforward job, thousands of dollars saved and a good-as-new spare transmission securely fixed to the aft stateroom floor under the companionway, ready to drop into place.

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The author, Peter Quentrall-Thomas (quentrall@gmail.com), was last seen fishing for piranha in the Orinoco Delta where he is currently exploring the rivers of South America on the historic motor yacht Passagemaker. You can read more at www.passagemaker.org.

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